1. Field of the Invention
The invention is related to packet network technologies, and in particular, to packet differentiation services.
2. Description of the Prior Art
Packet based communication networks package and transmit communications based on packet protocols. Recent advances in packet based communications have resulted in an expansion of packet based voice communication networks. Voice over Internet Protocol (VoIP) typifies modern packet based voice communication protocols. VoIP networks digitize, compress, and convert voice communications to IP packets. Most VoIP networks include network elements such as media gateways and locations servers. Media gateways extend VoIP calls between and across network domains. Location servers have responsibility for controlling media gateways and tracking the location and status of media gateways. Specialized signaling protocols are employed by media gateways and location servers to set up and tear down VoIP calls and to locate and track media gateways.
Session Initiation Protocol (SIP) is an example of a popular VoIP signaling protocol well known to those skilled in the art. SIP provides advanced signaling and control to VoIP networks for initiating, managing, and terminating VoIP network sessions, or calls. A typical SIP enabled VoIP network includes proxy servers which run the location servers. Such a network also includes user agents and media gateways.
User agents are the end users of a SIP network. For example, a SIP enabled phone is a user agent. User agents can be the origin or destination for a call over a VoIP network. Media gateways interwork communications between network domains. Often times, media gateways interwork communications between a VoIP network and the public switched telephone network (PSTN). Other times, media gateways interwork communications between two VoIP networks or otherwise packet based networks.
Proxy servers (also sometimes referred to as media gateway controllers) provide registration, redirect, and location services implemented by registrar, redirect, and location server applications running on the proxy servers. In particular, registrar servers manage user agents assigned to their network domains. Redirect servers redirect SIP messages to their appropriate destinations and return location information in response to queries. Location servers share responsibility for knowing the location and status of each gateway.
Telephony Routing over Internet Protocol (TRIP) is a well known protocol established to effectuate messaging between location servers and gateways to keep track of the location and status of the gateways. TRIP does not run directly over IP—it must ride over a telephony protocol like SIP or H.323. IP does not provide the infrastructure (e.g. SIP proxy server and media gateway) nor the packet structure to provide what TRIP needs to do its very specific job (dynamic building of proxy server routing tables). In a SIP only network, location servers are not utilized; rather, the proxy server will use standard Domain Name Service (DNS) methods to determine where to forward call requests. In a TRIP enabled SIP network, the location server builds a dynamic routing table based on TRIP update messages transmitted from various media gateways and location servers. The location server then accesses the resulting TRIP routing table to determine where to forward and redirect call requests.
TRIP enabled location servers are often referred to as TRIP speakers. A scaled down version of TRIP called TRIP-lite can be implemented on gateways. TRIP-lite transmits messaging from a gateway to at least one location server advertising the available routes and prefixes accessible through that gateway. For example, a first TRIP-lite enabled gateway might advertise to a location server that it services the 913 area code of the public switched telephone network (PSTN), while a second TRIP-lite enabled gateway advertises to the location server that it services the 816 area code of the PSTN. Thus, when a call request indicating a PSTN area code of 913 arrives into the location server, the location server knows to route that call to the first TRIP-lite enabled gateway. Other attributes advertised by TRIP-lite enabled gateways include destination prefixes, capacity to each prefix destination, and utilization levels of each trunk group terminating at the gateway, as well as other attributes. TRIP-lite allows location servers to have real-time knowledge of available gateway resources.
Unfortunately, current VoIP networks do not provide traffic conditioning capabilities for TRIP messaging. In the prior art, services such as Differentiated Service (DiffServ) use type of service (ToS) indicators to indicate a class of service to be implemented for different types of traffic. For example, voice traffic receives a higher class of service than data traffic. However, such traffic conditioning in the prior art does not differentiate between voice and data traffic and TRIP update messages. Furthermore, such traffic conditioning does not differentiate between the various types of TRIP update messages. Thus, VoIP network elements apply a constant class of service to all types of TRIP traffic regardless of the type of traffic. The current situation leads to undesirable periods of traffic congestion in network elements.